1r63
From Proteopedia
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STRUCTURAL ROLE OF A BURIED SALT BRIDGE IN THE 434 REPRESSOR DNA-BINDING DOMAIN, NMR, 20 STRUCTURES
Overview
The independently folding 63-residue N-terminal DNA-binding domain of the, 434 repressor, 434(1-63), contains a buried Arg10-Glu35 salt bridge. A, corresponding salt bridge is found in a variety of prokaryotic and, eukaryotic DNA-binding proteins with helix-turn-helix motifs. Here, the, NMR solution structures of 434(1-63) and the mutant protein, 434[R10M](1-63) were determined to investigate the structural role of this, salt bridge. Both proteins contain the same type of global fold, with five, alpha-helices and a helix-turn-helix motif formed by the helices II and, III. The primary structural difference caused by the Arg10 --> Met, mutation is a translation of helix I along its axis relative to the helix, II-turn-helix III motif. This limited conformational change is paralleled, by a 9 kJ M(-1) decrease of the stability of the folded mutant protein in, aqueous solution at pH 4.8. It affects the pKa value of Glu19 as well as, the population of a hydrogen bond between the backbone amide proton of, Asn16 and the side-chain carboxylate group of Glu19. Using the crystal, structure of the 434 repressor dimer complexed with the operator DNA as a, basis, model building of the DNA complex with the NMR structure of, 434[R10M](1-63) shows that Asn16, which is located on the protein surface, makes direct contact with the DNA and indicates that the point mutation, Arg10 --> Met should also lead to modifications of the protein-protein, contacts in the complex.
About this Structure
1R63 is a Single protein structure of sequence from Bacteriophage 434. Full crystallographic information is available from OCA.
Reference
Structural role of a buried salt bridge in the 434 repressor DNA-binding domain., Pervushin K, Billeter M, Siegal G, Wuthrich K, J Mol Biol. 1996 Dec 20;264(5):1002-12. PMID:9000626
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